oh mmmhhh… I can only tell you what the most difficult things are for people to grasp, maybe you can be especially aware of those…
1. the articles and the gendering of everything; it does not make sense a lot of the time but it’s just how things work over here. Like a desk being female and a soccer ball being male. It’s not something you can work out logically; it’s really just a matter of learning it by heart.
2. the cases which change the appearance+sounds of the articles (and some words)… they’re also tricky to learn but there are not many…
so I guess what I’m saying is, there’s a lot that does not make sense and has to be learned by heart so don’t get discouraged, just push your way through 🙂

You know, I was actually thinking door but typed desk. You are correct, of course.
Just to clarify:
Die Tür – the door (fem.)
Der Tisch – the desk (masc.)
Der Ball – the ball (masc.)